Along with the popularization of the mobile communication technology, mobile communication terminals gradually come into people's daily lives. As an important part of mobile communication terminals, the SIM (Subscriber Identity Model) card in the mobile communication terminals is broadly used. Along with the continuous development of the technology, to meet the increasing requirements of users' experiences on mobile communication terminals, a SIM card with multiple new functions is developed and is put into use. A radio-frequency SIM card with low-frequency magnetic communication is one of the examples.
The radio-frequency SIM card with low-frequency magnetic communication is a SIM card with functions of low-frequency magnetic communication and radio-frequency communication. It comprises a card body and an integrated circuit in the card body. The card body of the radio-frequency SIM card with low-frequency magnetic communication comprises a SIM card interface that matches with a mobile communication terminal. The integrated circuit in the card body comprises: a central processing unit (CPU); a low-frequency magnetic induction circuit and a low-frequency magnetic information receiving module that are electrically connected with the CPU; a SIM card memory, a radio-frequency transceiver circuit, and an interface circuit that are electrically connected with the CPU; and a radio-frequency transceiver antenna electrically connected with the radio-frequency transceiver circuit. The radio-frequency SIM card with low-frequency magnetic communication is electrically connected, through its own interface circuit and the SIM card interface on the card body, with a mobile communication terminal. The radio-frequency SIM card with low-frequency magnetic communication not only can communicate with the mobile communication terminal to realize functions of a normal SIM card but also can conduct short-distance communication with matching external processing devices (e.g. a card reader) through the low-frequency magnetic induction circuit, the low-frequency magnetic information receiving module, the radio-frequency transceiver circuit, and the interface circuit. The process and content of the short-distance communication is processed specifically by the central processing unit CPU inside the radio-frequency SIM card with low-frequency magnetic communication.
The radio-frequency SIM card with low-frequency magnetic communication is mostly used in a mobile phone. Besides all the functions of a normal SIM card, it can also allow the mobile phone to have the functions of smart cards such as a public transit card, an entrance guard communication card, a credit card, a small-amount payment card, and a time card. Moreover, the information generated when the various smart card functions are used can be displayed directly on a screen of the mobile phone and the user can accomplish the various operations through a keyboard of the mobile phone.
When a radio-frequency SIM card with low-frequency magnetic communication is used as smart cards such as a public transit card, an entrance guard communication card, a credit card, a small-amount payment card, and a time card, to avoid misreading operations, a distance for a mobile communication terminal having the radio-frequency SIM card with low-frequency magnetic communication to carry out an effective data transmission with a card reader, i.e. a transaction-triggering distance, must be controlled to a certain range. In addition, when the SIM card enters such a transaction zone, the transaction-triggering speed shall not be too slow; otherwise, the use effect of the user will be affected.
It is a fact that a radio-frequency SIM card with low-frequency magnetic communication needs a long time to receive information of the low-frequency magnetic field during the use resulting from a low communication rate of a low-frequency alternating magnetic field. How to maximize the reliability of a transaction-triggering distance while overcoming the problem of an excessive long transaction-triggering time caused by such fact is important and urgent for realizing an application of a radio-frequency SIM card with low-frequency magnetic communication. Meanwhile, minimizing the user's transaction time is also important.